Before anyone starts, yes I know what octane is a measure of.
From when I bought the BD used in February I've been using regular (87) and not thinking anything about it. When I last filled up I accidentally (really, it was an accident) grabbed the wrong handle and put in 89.
The surprising thing to me is that this NA car seems to be running better then before.
I wasn't expecting any improvement, but low-end hesitation is gone now.
Am I just imagining things or should I have been using a higher octane all along?